Light detector with cleaning and testing means

ABSTRACT

A furnace flame detector having a light-sensitive tube which can be periodically wiped clean and blocked off from the flame light to be tested. A web has a wiper section in contact with the tube and is connected with an actuating mechanism for periodically moving the wiper section over the tube. The wiper section has a centrally located aperture which permits the flame light to impinge on the sensing tube, so that when the wiper section is moved over the tube, it is cleaned and the flame light is intermittently blocked off to permit the tube to be tested.

United States Patent William J. Moore;

Donald J. L. Lin, both of Dallas, Tex. [2]] Appl. No. 850,603

[22] Filed Aug. 15,1969

[45] Patented Sept. 28, 1971 [73] Assignee Forney Engineering Company Dallas, Tex.

[72] Inventors [54] LIGHT DETECTOR WITH CLEANING AND 3,021,386 2/1962 Clark 431/79 X 3,286,761 ll/1966 Engh 431/79 UX 3,437,816 4/1969 Mushinsky 250/232 X ABSTRACT: A furnace flame detector having a light-sensitive tube which can be periodically wiped clean and blocked off from the flame light to be tested. A web has a wiper section in contact with the tube and is connected with an actuating mechanism for periodically moving the wiper section over the tube. The wiper section has a centrally located aperture which permits the flame light to impinge on the sensing tube, so that when the wiper section is moved over the tube, it is cleaned and the flame light is intermittently blocked off to permit the tube to be tested.

PATENTEI] m8 ISYI INVEN'I'ORS WILLIAM J. MOORE DONALD J. L. LIN BY I Q1? MA JOHN E. WILSON ATTORNEY LIGHT DETECTOR WITH CLEANING AND TESTING MEANS BACKGROUND OF THE INVENTION In a modern steam generator, the loss of flame at a burner decreases efficiency andlowers the energy output. In addition, a boiler tube may be damaged because it will not receive enough heat to vaporize the water in it. In passing to the vapor stage, the water cools the tube much more than it would, by merely passing through the tube without changing to steam, as it does when deprived of heat.

To guard against such mishaps, sensing elements are provided in the steam generator to detect a loss of flame at the burners. The sensing elements are sensitive to the flame light and are each positioned so that the light from a flame impinges against it. If a burner should lose its flame, a sensing element will either transmit a signal or discontinue signal transmission to shut down the generator or indicate to an operator that the boilerv should be shut down until the defective burner is repaired.

One problem which has been encountered is that the high temperatures in the portion of the steam generator adjacent to the burners may eventuallymake the sensing elements too insensitive to detect a loss of flame. In order to solve this problem, flame detectors have been cooled by providing a stream of cooling air in the manner described and claimed in U.S. Pat. Ser. No. 719,768, which was filed on Apr. 7, 1968 in the name of William J. Moore, now Pat. No. 3,437,807 and assigned to Foster Wheeler Corporation and which issued on Apr. 8, I969 as US. Pat. No. 3,437,807. Still another problem is created by the soot and other matter present in the burner area, which will tend to coat the sensing element so that it will not be able to correctly detect a loss of flame.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the problems found in the prior art such as those discussed above. Accordingly, a light-sensitive tube is engaged by a belt having a wiper section. The belt is provided with an aperture at the wiper section and an actuating mechanism, to move the section back and forth over the tube to clean it and move the aperture to intermittently block off the flame light to permit the tube to be tested.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a portion of a light detector assembly made in accordance with the present invention;

FIG. 2 is a view partly in section in a scale larger than that of FIG. 1 of the present assembly; and

FIG. 3 is a detailed view of the wiper web and its associated spring used in the assembly ofFlGS. l and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT The assembly shown in FIG. 1 and designated as includes a base 12 and solid body portions 14 extending forwardly therefrom. Extending forwardly from the body portions 14 are arms 16 which are parallel to the longitudinal axis of the device. Although only one arm 16 can be seen in FIG. 1, another extends parallel to it along the obscured side of the device. A light-sensitive element or tube 18 is mounted at the free ends of arms 16 by means of screws 20, each of which extends through an ear 22. integral with flange 24 of the tube 18.

The assembly is positioned in a housing 26 (FIG. 2) which includes a generally cylindrical cover 28 extending outwardly from the base 12 to an annular collar 30 at its opposite end. The annular collar 30 encircles an annular ring 32 which defines an orifice 34 which permits light from the flame 36 to communicate with the tube 18.

In order to assure that the tube 18 will not be heated to such a high temperature that it is insensitive to the presence of the light from the flame 36, cooling air moving in the direction of the arrows 38 is forced through the housing 26 and out the orifice 34 to cool the tube 18.

It has been explained that in the past, the accumulation of soot and other matter on the tube 18 has prevented it from functioning correctly. It has also been explained that in order to ascertain that the tube 18 is functioning properly, it is blocked off from the flame light from time to time to be sure that it will sense and signal the absence of light. Both of these functions are carried out in the present invention by means which include a flexible web 40 (FIG. 3) having a straight portion 42, a wiper section 44'and a straight portion 46. The more or less straight portions 42 and 46 merge with, and extend rearwardly from the wiper section 44. An orifice 48' located centrally in the wiper section 44 permits the light to pass from the flame 36 to the tube 18. When the web 40 is operated to test and clean the tube 18, the portions 42 and 46 are each reciprocated so that the portion 42 moves forward while the portion 46 moves to the rear and vice versa. This action moves the wiper section 44 and its associated orifice 48 back and forth over the tube 18 so that light from the flame 36 is intermittently blocked off from the tube 18. The tubes sensitivity to the light can be tested during this times, because it will if it is functioning properly, signal alternately the presence and absence of flame light. Movement of the wiper section 44 over the tube 18 will also wipe it clean of soot or other matter which have an adverse effect upon its sensitivity. The matter which is removed from the tube 18 will be blown out of the orifice 34 bythe cooling air moving in the direction of the arrows 38.

The web 40 is oscillated by means of linkage which includes an elongated member 50 at the rear end of the straight portion 42 and a coil spring 52 secured to the rear end of the straight portion 46. The rear end of the member 50 includes a hole 54 at which the member 50 is pivoted to a link 56. The link 56 extends generally in a vertical plane, its upper end being pivoted to the member 50 and its lower end being pivoted at a point 58 which is fixed with respect to the body portions 14 of the device 10. The rearward end of the coil spring 52 is also fixed with respect to the body portion 14. The link 56 is pivoted at a point pivot 60 between its ends with a piston rod 62 which extends rearwardly to a piston 64 which is slideably positioned within a cylinder 66. The piston 64 is urged rearwardly by a coil spring 68 which extends in the cylinder 66 around the piston rod 62 and between the piston 64 and a forward wall 70 of the cylinder 66. When compressed air is intermittently supplied to the rear surface of the piston 64, it will reciprocate against the spring 66 to oscillate the link 56 about the pivot point 58 through the piston rod 60. This in turn will reciprocate the member 50 which will push and pull the section 42 to move the wiper section 44 back and forth over the tube 18. The straight portion 46 will reciprocate with the wiping section 44 but will be held taut by the spring 52 to assure that the wiper section 44 is held in contact with the tube 18.

It will be appreciated that the foregoing describes but one preferred embodiment of the present invention and that other embodiments are possible without exceeding its scope.

We claim:

l. A light-detecting apparatus havinga light-detecting element which may be tested and cleaned periodically comprising a flexible web having a wiping section engaging said element, said section having an aperture which permits light to pass through said web and impinge upon said element, and means to move said web in relation to said element so that a portion of it always engages against said element so that light is alternately blocked and allowed to pass through said aper' ture to permit said element to be tested while said web removes soot or other matter from said element.

2. The apparatus defined in claim 1 wherein, said means engages said web atone of its ends.

3. The apparatus defined in claim 2 wherein, the other end of said web is engaged by a spring which permits said web to oscillate under the action of said means while urging said wiping section against said element.

4. The apparatus defined in claim 2 wherein, said web has ends which extend rearwardly of said element.

of said web is connected with a spring which permits said web to oscillate while urging said wiping section against said element. 

1. A light-detecting apparatus having a light-detecting element which may be tested and cleaned periodically comprising a flexible web having a wiping section engaging said element, said section having an aperture which permits light to pass through said web and impinge upon said element, and means to move said web in relation to said element so that a portion of it always engages against said element so that light is alternately blocked and allowed to pass through said aperture to permit said element to be tested while said web removes soot or other matter from said element.
 2. The apparatus defined in claim 1 wherein, said means engages said web at one of its ends.
 3. The apparatus defined in claim 2 wherein, the other end of said web is engaged by a spring which permits said web to oscillate under the action of said means while urging said wiping section against said element.
 4. The apparatus defined in claim 2 wherein, said web has ends which extend rearwardly of said element.
 5. The apparatus defined in claim 4 wherein, said means comprises a piston connected with said one end, said piston being slideable to reciprocate said one end.
 6. The apparatus defined in claim 4 wherein, the other end of said web is connected with a spring which permits said web to oscillate while urging said wiping section against said element. 